Best way to flush heater core only?

[Number_35]

Guys -

A few years ago I chose to use a cracked block/HG sealer in my old van's cooling system in preference to tearing down my engine. (I had taken it to the dealership for a 2nd opinion, and was told it was likely a cracked head.) It didn't slow down the coolant leak, but did plug the heater cores (front & rear).

Last Fall I finally tore things down far enough to find loose intake manifold bolts. I replaced the steel gaskets while I was in there, and that solved the coolant leak. I likely would have been OK just retorquing them.

While everything was apart, I also disconnected the inlet & outlet to the heater cores, and extended them with generic heater hoses. I elevated the hoses, poured in white vinegar, and let things sit overnight. Flushed the heater cores both ways with a garden hose, and put everything back together.

The heat definitely seemed improved when it was around freezing, but was still poor in mid-winter (c. -35 C).

I've just changed the thermostat (which was getting a bit lazy, per the ScanGauge) and noticed the old one was covered with a hard, brittle deposit. That was likely the block sealer.

I'd like to do another soak with something that will help dissolve the hard junk without harming the heater cores.

I'm thinking perhaps pure lemon juice this time, but am very open to suggestions.

Your input is most appreciated!

 

[Chris142]

Remove heater hoses. Flush with air and water,put hoses back on.

 

[earlyre]

if we're talking mineral deposits(lime scale, etc ie:hard water stains),denture tabs can work wonders on things like vases,fishbowls,showerheads, etc...

I like to think a little outside the box sometimes.

 

[Number_35]

Originally Posted By: Chris142
Remove heater hoses. Flush with air and water,put hoses back on.


Chris - Did that a few days ago. Water runs freely in both directions. Got very little debris out. I suspect the layer of sealer acts as a thermal insulator. I need something to dissolve or at least soften it.

 

[mongo161]

IMO....put some old hoses on the inlet and outlet of the heater core and pour some boiling hot, dissolved automatic dishwasher powder solution into the heater core and let it sit overnight. Flush the next day with hot water from your home's hot water heater.....back and front flushes until the water runs clean.

 

[JTK]

If you're getting really good flow through the heater cores when you flush them, it would seem to me enough tubes are free and clear in the cores to transfer heat. Are you sure the T-stat is all good?

 

[Rand]

I'd try the dishwasher flush or http://shop.advanceautoparts.com/p/peak-radiator-super-cleaner-and-flush-32-fl.-oz.-pkf0ae/7690005-P

 

[Number_35]

Originally Posted By: JTK
If you're getting really good flow through the heater cores when you flush them, it would seem to me enough tubes are free and clear in the cores to transfer heat. Are you sure the T-stat is all good?


I'm sure the old T-stat was tired; per the ScanGauge, the coolant was only hitting the mid-80s (C) in the winter, and taking its time to get there. The thermostat is spec'ed to start opening @ 82 C, and to be fully open @ 96 C. Ten or 12 years ago, the temperature would hit the low 90s, even on a cold winter day. So, yes, that would be part of it, but not the whole story.

 

[Number_35]

Originally Posted By: earlyre
if we're talking mineral deposits(lime scale, etc ie:hard water stains),denture tabs can work wonders on things like vases,fishbowls,showerheads, etc...

I like to think a little outside the box sometimes.


That is outside the box! I like it, may try it. Would likely be easy on aluminum.

 

[Number_35]

Originally Posted By: mongo161
IMO....put some old hoses on the inlet and outlet of the heater core and pour some boiling hot, dissolved automatic dishwasher powder solution into the heater core and let it sit overnight. Flush the next day with hot water from your home's hot water heater.....back and front flushes until the water runs clean.


Read some old posts which say that the new phosphate-free detergents are not as effective as the old ones were. May try it anyway.

 

[Benito]

Get yourself a cheap pump and rig the hoses to constantly circulate the detergent / water through the core.

Agitation improves the efficacy of most detergents.

 

[DoubleWasp]

Originally Posted By: Benito
Get yourself a cheap pump and rig the hoses to constantly circulate the detergent / water through the core.

Agitation improves the efficacy of most detergents.


Use this method, except circulate 4 parts water and 1 part Bright Bay Hammerhead Marine Descaler.

I've used this method to clear worse [censored] than what you're dealing with.

 

[joegreen]

I always like when someone tries to fix what they have instead of buying new but have you thought about new heater cores. They are not much money.

 

[Kuato]

If you are removing scale deposits, you may want to consider CLR. Though not originally meant for automotive use it is H on wheels on scale. You may want to flush with straight water beforehand, unless you are a chemist and know how it will react with the coolant.

 

[Number_35]

Originally Posted By: joegreen
I always like when someone tries to fix what they have instead of buying new but have you thought about new heater cores. They are not much money.


Joe - Good thought. It's not the cost of the heater core, it's the 10 hours labour. Would likely take me longer the first time.

 

[Number_35]

Originally Posted By: DoubleWasp
Originally Posted By: Benito
Get yourself a cheap pump and rig the hoses to constantly circulate the detergent / water through the core.

Agitation improves the efficacy of most detergents.


Use this method, except circulate 4 parts water and 1 part Bright Bay Hammerhead Marine Descaler.

I've used this method to clear worse [censored] than what you're dealing with.


I was thinking of trying to rig up something like this!

 

[Number_35]

Originally Posted By: Kuato
If you are removing scale deposits, you may want to consider CLR. Though not originally meant for automotive use it is H on wheels on scale. You may want to flush with straight water beforehand, unless you are a chemist and know how it will react with the coolant.


Old posts indicate that CLR works great, but can be very hard on aluminum. I've just come in from draining the coolant, flushing out the cores with hose water, blowing out the water, and filling with pure lemon juice. Will leave it 24 hours and see what comes out. As a control, I've got the old thermostat immersed in a glass of the same lemon juice. Will see if the overnight soak cleans it up.

Will consider CLR if the lemon juice doesn't do it.

Thanks, everyone, for your suggestions. Stay tuned!

 

[Bluestream]

Lemon Juice? That has to be a first!

 

[Number_35]

Originally Posted By: Bluestream
Lemon Juice? That has to be a first!


Hey, it was in the fridge! Almost a full quart. Saved me a trip to the store. Feels more acidic on my cut-up hands than the vinegar did last year. Hopefully will cut through the scale.

 

[Brybo86]

CLR flush I did on my Honda a few months ago